Method of producing a multidimensional composite image

ABSTRACT

Multi-dimensional lithographs which impart the illusions of depth and/or motion to a viewer are prepared by constructing and sequencing a plurality of electronic pages, preferably four or more; rasterizing, compressing and converting each page; interlacing the pages in a desired sequence; outputting the interlaced frames to an imaging device; and producing a lithographic separation from the imaging device. In the rasterization of each frame, nonbinary pixels are created that correspond to the resolution of the line count of the lenticular lens that will ultimately be applied to a print of the lithograph times the number of frames in the lithographic separation. The frames are compressed to an amount equal to the reciprocal of the number of frames from which the lithographic separation is prepared. In the converting step, the nonbinary pixels of the compressed frames are converted to individual color plates of binary pixels. The multidimensional lithographic separations are free of moire and screen interference.

This application is a continuation of application Ser. No. 08/593,252,filed Jan. 29, 1996, now U.S. Pat. No. 5,617,178.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to lithography. In one aspect, the inventionrelates to a method of producing multidimensional lithographicseparations while in another aspect, the invention relates to a methodof producing such separations free of moire interference. In yet anotheraspect, the invention relates to producing lithographic motion pictures.

2. Description of the Related Art

Lithography is an old, well-known and well-practiced art. In its firstlife, lithographs were created by drawing on the surface of a limestoneslab with an oily wash or greasy crayon. The surface was then washedwith an acid such that the marked areas of the surfaces rejected waterbut retained ink. The stone was then set within a press and when broughtin contact with paper, it printed the paper with the inked image. Withinfifty years of its first development, metal plates began to replace thelimestone slabs. Today, rotary presses have replaced flatbed presses,paper and plastic plates are in use, and the use of color inkscommonplace.

As lithography grew in sophistication, so did its varied uses.Originally a technique of printing, with time it grew into a popularmedium for artists. Where the first images were created by hand, todaythe images can be created by one or more of a wide variety oftechniques, e.g., photographic, chemical etching, computer-controlledoptical scanning and engraving, digital art, and the like. Modern daylithographs are ubiquitous in the print and advertising industries, aswell as many others.

Historically lithographs were two dimensional creations like any otherpicture or photograph. Perception of depth was dependent upon thecontent of the picture itself. However as described in U.S. Pat. No.5,266,995 to Quadracci, et al., three dimensionality can be imparted toan image by first creating the image with a special stereoscopic cameraand then overlaying the image with a lenticular lens sheet. Both thestereoscopic cameras and lenticular lens sheets are known in the art andare commercially available. U.S. Pat. No. 5,113,213 to Sandor, et al.teaches a method of preparing three dimensional lithographs through theuse and manipulation of computer images. In this technique, the imagesare interleaved into a predetermined number of planar images, and thenprinted with a high-resolution output imaging device on a spacer, and aselected edge of each interleaved image is aligned with a predetermineddirection of the spacer.

However imparting the fourth dimension, motion, to a static pictureremains absent in the art.

SUMMARY OF THE INVENTION

According to this invention, multidimensional lithographic separationsare prepared in a manner which can convey the illusions of depth and/ormotion. As here used, "multidimensional lithographic separations" meansseparations that are three dimensional (depth) or four dimensional(motion, with or without depth). These separations are prepared by amethod comprising the steps of:

A. Creating a plurality of electronic frames;

B. Ordering the frames into a desired sequence;

C. Rasterizing each frame at a nonbinary pixel resolution thatcorresponds to the resolution of the line count of a lenticular lenstimes the number of frames in the lithographic separation;

D. Compressing each frame such that the compres-sion of each frame is afunction of the number of frames in the lithographic separation;

E. Converting the nonbinary pixels of the com-pressed frames toindividual color plates of binary pixels;

F. Interlacing the frames in the desired sequence;

G. Transferring the interlaced frames to an imaging device; and

H. Producing a lithographic separation from the imaging device of stepG.

The lithographic separations produced by the method of this inventionare free of moire and screen interference and when viewed through thelenticular lens for which they were designed, impart an illusion ofdepth and/or motion to a viewer.

The concept of a lithographic motion picture, i.e., a lithograph thatimparts the illusion of motion, can be explained by reference to motionfilms. These films consist of a series of still pictures and if thesepictures are projected in the proper sequence and at the properfrequency (24 frames per second), then the illusion of motion iscreated. The human brain perceives real motion from a series of stillpictures.

Lithographic motion pictures consist of a series of still pictures. Theindividual pictures are segmented, typically into columns, and theindividual columns are then merged together in a desired sequence toform a composite picture or image. This segmenting and merging isaccomplished with the use of a computer, and the composite picture isthen outputted to a lithographic separation, e.g., a film, proof, etc.Once the composite image is transferred to any suitable substrate, e.g.,paper stock, a lenticular lens is laminated to its surface. The lens(which is typically an array of identical spherically-curved surfacesembossed or otherwise formed on the front surface of a plastic sheet)refracts light from each picture in sequence as the viewer's angle ofperception changes. The result is the perception of motion from a seriesof still pictures. The illusion of depth is created in a similar manner.

The lithographs of this invention can tell a story, show events overtime, and an objective in perspective. The process of this invention isa direct lithographic process in that the creation of intermediateimages is not required, thus eliminating the need to create intermediateart which would later require separation from the final composite image.Moreover, the process of this invention does not require the use ofspecial dimensional cameras or photographic techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of four base images in sequence.

FIG. 2 is the sequenced base images of FIG. 1 segmented into columns ofequal width.

FIG. 3 is an illustration of a sequence of frames comprising segments ofthe base images illustrated in FIGS. 1 and 2.

FIG. 4 is a schematic depiction of the frames of FIG. 3 compressed toregister with the lenticulas of a lenticular lens.

DETAILED DESCRIPTION OF THE INVENTION

The lithographic separations of this invention are a composite of aseries of still pictures or frames. The frames begin as eitherconventional print or art, e.g., text, photographs, etc., which areconverted into electronic data, e.g., by optical scanning, etc., or arefirst created electronically, e.g., through the use of a software artprogram, a word processing program, etc. Once in electronic form, theframes are ordered in a sequence which will impart the desired illusionwhen the final lithographic print is joined to a lenticular lens. Afterordering, each frame is preferably saved in a software file, e.g., aPOSTSCRIPT™ file, rasterized, compressed, and then converted fromnonbinary pixels to binary pixels. Once converted, the frames are theninterlaced with one another in the desired sequence to form a compositepicture or image, and then the composite picture is outputted to animaging device, preferably a high-resolution imaging device. Theresulting product is typically a film or proof which can be used toproduce prints of the composite image which ultimately are joined to alenticular lens. The "joining" is typically the lamination of the lensto the surface of the image, but this, invention includes the printingof the composite image on the back or flat side of the lenticular lensitself. In this manner, the final lithograph can be displayed to aviewer through the use of back-lighting.

Lenticular lenses are known and commercially available. These lensestypically consist of an array of identical spherically-curved surfacesembossed or otherwise formed on the front surface of a plastic sheet(although other geometric patterns are known, e.g., pyramidical, andthese too can be used in this invention). Each individual lens orlenticule is a long cylinder which typically extends the full length ofthe underlying image to which it is laminated. The back surface of thelens, i.e., the surface of the lens in contact with the underlyingimage, is flat.

In the conventional production of a computer-generated lithograph orlithographic separation, an electronic page is created. The pageconsists of a collection of page elements that are arranged in a desiredorder. The elements can be drawn from a wide variety of sources, e.g.,photographs, original artwork, type, etc. The electronic page is thenoutputted to a half-tone film separation, i.e., a film bearing an imageof the electronic page in a half-tone screen. Half-tone screens consistof an array of dots varying in size in relation to the tonal values ofthe elements of the page. These conventional lithographs are twodimensional, i.e., they possess length and width but not depth ormotion.

Lithographs with three dimensionality can be produced by photographic orcomputer-generated interlacing methods, but these methods suffer fromproblems of moire and screen interference. These methods are more fullydescribed in U.S. Pat. No. 5,266,995 and 5,113,213.

Moire interference is an undesirable pattern resulting from theoverlapping of two or more grid patterns including the halftone dots ina film separation.

Screen interference is the broken appearance of detail, lines or imageedges caused by halftone dots that are too coarse in comparison to theline or edge being drawn by the halftone dots. Screen interference isalso known as stair-stepping or jaggies. The appearance of screeninterference within an image is often interpreted as a moire. Imagescontaining repetitive lines often exhibit this type of interference, forexample fabrics, pin stripping, etc. The lines created in theinterlacing phase of the current three dimensional methods are a majorsource of moire and screen interference.

In this invention, stochastic or frequency-modulated techniques areemployed which virtually eliminate moire and screen interference. Thisimprovement is the result of a direct pixel to pixel relationship.Stochastic screening yields a resolution which is four times greaterthan that of a conventional halftone dot because each quadrant of theconventional halftone dot is produced as an individual spot. Stochasticscreening eliminates the merging of four pixels into a single dot,screen rotation and the formation rosette patterns.

In order to impart the illusion of depth and/or motion to a staticimage, the image must be made from more than one picture or frame.Typically, at least three, preferably four or more, pictures areinterlaced with one another in any desired sequence to form a compositeimage or picture that when viewed through a lenticular lens, imparts theillusion of depth and/or motion to the viewer. In the creation of thecomposite picture, the base images or still pictures from which thecomposite is formed can consist of essentially anything that can bereduced to digital information or pixels, or anything that can becreated electronically. Illustrative base images include photographs,graphics, type, logos, animation, video, computer-generated or digitalart, vignettes, tints, dimensional art, graphs, charts and similarinformation. Information not originally in electronic form can beconverted to electronic form, as noted above, by any conventionaltechnique.

Once all of the information that is to be included in the compositeimage is in electronic or pixel form, then an electronic page iscreated, typically through the use of any commercially availablesoftware package, e.g., QuarkXPress, manufactured and sold by Quark,Inc. of Denver, Colo. One page is created for each frame from which thecomposite image will be generated. Once each electronic page isassembled, then the pages are ordered into a desired sequence, i.e., thesequence that will impart the desired illusion to a viewer of thecomposite image once joined to a lenticular lens.

After the electronic pages are assembled and ordered, then preferablyeach is saved in a software file, e.g., in a file type such asPOSTSCRIPTS™. Saving is preferred because many page assembly programs donot allow for the direct conversion of the page to a rasterized file.However in those page assembly programs that allow for such directconversion, this saving step can be omitted.

Whether saved or not, each assembled page is then rasterized, i.e., itis converted into a pixel array. This process can be accomplishedthrough any one of a number of different software raster imagingprocessing (RIP's) programs, e.g., Freedom of Press Prom™ manufacturedand sold by Color Age. Each frame is rasterized at a nonbinary pixelresolution or depth that corresponds to the resolution of the line countof the lenticular lens times the number of frames used to create thelithographic separation, i.e., the number of frames or pictures fromwhich the composite image is created. This relationship can be expressedas

    resolution=1 times f

in which 1 is the line count of the lenticular lens and f is the numberof frames in the lithographic separation. The line count of thelenticular lens can vary, and is typically between fifty and two hundredlines per lineal inch, preferably about seventy-five lines per linealinch. "Line count" is the number of lenticules per lineal inch of thelenticular lens.

As here used, "nonbinary pixels" are pixels that have a depth of one ormore, and that can be expressed as black, a value of grey or color, orwhite. "Binary pixels" are a subset of nonbinary pixels, and these havea depth of one and as such, can only be expressed as black or white,i.e. on or off.

The rasterized frames are then compressed such that the compression ofeach frame is a function of the number of frames in the lithographicseparation. Compression is expressed as the reciprocal of the number offrames per line or lenticule, i.e.,

    Compression=1/f

where f is the number of frames in the composite image. This techniqueretains most, if not all, of the frame information, i.e., little or noneof the frame information is lost (although some may be subject to minordegradation), and when viewed through a lenticule, most, if not all, ofthe original information in the frame is conveyed to the viewer in anessentially noncompressed state or in other words, in a state in whichit has been expanded back to or near its original size.

The nonbinary pixels of the compressed frames are then converted toindividual color plates of binary pixels. In conventional halftonescreening, the number of dots per inch remain constant although the sizeof the dots can vary in relation to the tonal range density of the pixeldepth that they represent. Single halftone dots are represented by afour pixel square array, each pixel a quadrant of the square. Typicallya half-tone dot would have 256 possible values in which 256 is theequivalent of zero tone or clear, and zero is equivalent to solid orblack. In a color halftone separation, the individual color plates mustbe aligned on angles of varying degree so as to avoid moireinterference. Conventional angles are zero for yellow, 45 degrees formagenta, 75 degrees for cyan, and 105 degrees for black. Since anglescan be interchanged or skewed as a whole, dots composed of multiplepixels can create moire problems (essentially the result of therepetitive nature of the dissimilar pixels). Moreover, the angling ofthe halftone screens can result in a rosette pattern which in turn caninterfere with viewing through the lenticular lens creating screeninterference.

In stochastic screening, the tonal quality of an image is represented bythe frequency of the binary pixels which are all of like size. Thestochastic image resolution is tuned so that each segment of a compositepicture fits as precisely as possible within the width of the overlyinglenticule. This tuned stochastic screen in which a direct relationshipbetween pixels and lenticulas exists impart improved clarity andreproductive qualities to the composite image. This improvement is theabsence of fuzzy or gray areas caused by the interpolation of the dotstructure at points of transition from pixel to pixel, as well as theelimination of the rosette pattern which, as noted above, is a result ofthe merging of half-tone dots at off setting angles.

Since the stochastic screening method uses binary pixels, the need forregistration between the lenticulas and the segments of the compositeimage for the purpose of maintaining the desired perspective isessentially eliminated. In other words, the lenticule can be shiftedleft or right, or up or down, relative to the underlying compositesegment without adversely impacting the clarity of the image seen by theviewer through the lenticular lens. However, clarity still requiresparallel registration between the lenticulas and the segments of thecomposite, e.g., in those instances in which the lenticule is a longcylinder and the composite image segment is a column, the edges of thelenticule remain parallel with the edges of the column. Moreover,because the image sequence of the composite image changes pixel bypixel, a point of transition of one image into another is created whichin turn imparts the illusion to a viewer of an intermediate image. Thisillusion of an intermediate image imparts a more fluid motion than ifthe images were simply viewed in sequence, such as in a film.

After the nonbinary pixels of the compressed frames are converted toindividual color plates of binary pixels, the individual frames areinterlaced into a composite file. The frames are segmented, typicallyinto columns, the number of segments a function of the number oflenticulas in the lenticular lens which will eventually be laminated toa substrate bearing the compressed composite image. Correspondenceexists between each column within the segment and also between eachcolumn and the frame itself. In other words, if the composite imageconsists of four base images and each base image is divided into twentycolumns, typically each column of each base image of equal width, thenthe first segment of the composite image will consist of the firstcolumn of each base image, the second segment of the composite imagewill consist of the second column of each base image, and so forththrough the twentieth segment of the composite image.

Moreover, the sequencing of each column within each segment of thecomposite image is consistent with the sequence of base images in thecomposite image. For example, if the sequence of base images in thecomposite image is A, B, C and D, then this is the sequence of orderingof the columns in each individual segment of the composite image. *Thusin the first segment of the composite image, the first column of baseimage A is first, followed by the first column of base image B, followedby the first column of base image C, and finally followed by the firstcolumn of base image D.

The interlacing can be accomplished either by manual manipulation of thepixels, or through the use of a software program designed for suchinterlacing.

After the composite picture has been assembled, it is outputted at aresolution corresponding to its electronic resolution, and at a sizethat corresponds to the lenticular lens which will eventually overlayit. The composite image can be outputted to any high-resolutionoutputting device which can eventually create a lithographic separation,e.g., a film, proof, etc. This separation can then be used to create theprint to which the lenticular lens can be laminated by any conventionaltechnique. In one embodiment of this invention, the composite image isprinted directly to the reverse or back side of the lenticular lens suchthat the image is displayed to a viewer when subjected to backlighting.

Although the construction of a frame has been described from theperspective of columns, frames can also be constructed from theperspective of rows or other groups of pixels if particular effects aredesired. The digital base image is a series of pixels that can berepresented as a grid, and any segment of that grid can serve as abuilding block for a frame. For example, creating motion from an arrayof rows allows the composite image to be displayed in any perspectiveforward of the viewer, e.g. in an overhead, on a wall or billboard, in afloor panel, etc. As the viewer moves toward the display, regardless ofangle but preferably from a relatively perpendicular approach, theviewer perceives the intended motion.

This invention can produce lithographs of photographic quality thatimpart the illusion of motion and/or depth to a viewer. Theselithographs have many possible applications such as pages withanimations that move, movies condensed to a series of scenes that can beplayed repeatedly by the viewer, and point of purchase displaysincorporating motion graphics, images and animation.

As a further illustration of the lithographs of this invention and themethod of their preparation, reference is made to FIG. 1 in which fourbase images are illustrated, i.e., a circle, a rectangle, a square and atriangle. Each image is converted to digital information or pixels byany conventional technique and once converted, can be electronicallyretouched and manipulated as desired. These images are then sequencedand/or merged with other elements such as type, graphics, tints, and thelike (not shown) into a composite image or electronic page by anyconventional technique.

Each base image is then rasterized, compressed and converted fromnonbinary pixels to binary pixels (these steps not illustrated by thefigures). Each frame is then segmented as illustrated in FIG. 2, and theindividual segments then ordered into segments of the composite image.As illustrated in FIG. 3, the first segment of the composite imageconsists of the first segment of each of the base images in the order inwhich the base images are sequenced. The second segment of the compositeimage consists of the second segment of each of the base images, eachsegment of each base image positioned in the sequence in which the baseimages are ordered. This pattern repeats itself across composite image.

FIG. 4 illustrates that each segment of the composite image is in acompressed state such that it corresponds to the width of an individuallenticule of the overlying lenticular lens. The compressed compositeimage is then outputted to a film or digital proof from which thecomposite image is printed onto any suitable substrate, e.g., paper,metal, plastic, etc. The lenticular lens is then laminated to theimage-bearing surface of the substrate such that each lenticule is insubstantial parallel registration with each segment of the base image.Alternatively, the composite image is printed directly on the reverse orback side of the lenticular lens, again with each lenticule insubstantial parallel registration with each segment of the compositeimage.

Although only a few embodiments of the present invention have beendescribed above in detail, those skilled in the art will appreciate thatmany additions and modifications can be made without departing from thespirit and scope of the invention. These and all other modifications areintended to be included within the scope of the present invention asdescribed in the following claims.

What is claimed is:
 1. A method of producing a multidimensional imagecomprising a plurality of segments created from a plurality ofelectronic frames and from which a multidimensional image can beproduced and printed on a lenticular lens of a predetermined line count,the method comprising the steps of:A. Creating a plurality of electronicframes; B. Ordering the frames into a desired sequence; C. Rasterizingeach frame at a nonbinary pixel resolution; D. Compressing each frame;E. Converting the nonbinary pixels of the compressed frames to binarypixels; F. Interlacing the frames in the desired sequence of step (B);G. Outputting the interlaced frames to an imaging device; H. Producingan image from the imaging device of step G; and I. Lithographicallyprinting the multidimensional image.
 2. A multidimensional imageproduced by the method of claim 1.